The_High_Father
considering the mc is a magician, that he can have longer life force/stamina from killing, i recommend these divinities: of magic, of blood, war and slaughter since each is a method for him to gain lifeforce and stamina, finally, i recommend the god of life divinity since he uses life to strenthen himself, gain a healing factor etc. maybe he can get a death divinity too since he's gonna be killing people and the opposite of life is death, like yin and yang, together it'll make him stronger.